San Francisco prosecutors are tutoring local banks on how to recognize victims of the widespread Chinese blessing scams.

Foreign con artists who work in teams have duped dozens of spiritual Chinese women in The City into shelling out cash and jewelry to ward off bad luck, according to authorities.

The scams, believed to be part of an international crime ring, have been seen in multiple U.S. cities. Only in San Francisco have guilty verdicts been secured in such cases, said District Attorney George Gascón. But he said he believes the public information campaign his office has launched is a better way to combat the scam.

Last week, prosecutors met with the managers of several Chinatown banks to teach them how to identify possible victims. Employees are told to look out for customers who might withdraw all their savings on a random day or appear nervous and withdrawn. They also are informed to keep an eye out for scammers who might be waiting outside the bank, and are asked to display posters warning about the scam.

"Essentially we're doing a grass-roots movement," said Assistant District Attorney Marisa Rodriguez, who is directing the effort. "We need to reach the people who have a relationship with the community."

An instructional YouTube video is also in the works, Rodriguez said.

Rodriguez is one of the neighborhood prosecutors who have been deployed by Gascón to work closely within communities on various crime-prevention efforts.